The present invention relates to a closure for an opening of a coking oven in general, and more particularly to a closure to be used on a horizontal coking oven.
Coking ovens of this type are, of course, already known, and they include walls which bound a coking chamber, at least one charging and/or discharging opening being provided in such walls. It is also already known to provide a closure for such an opening, which usually includes a circumferentially complete frame mounted on the coking oven around the opening, and a door which is partially receivable in the frame and is adapted to be releasably and removably held in a closing position thereof by appropriate holding arrangements. The door is usually received in the opening with a clearance from the frame, and sealing arrangements are provided which seal the clearance and thus prevent escape of volatile by-products of the coking process from the coking chamber through the clearance between the door and the frame.
Experience with the conventional coking ovens having closures of this type has shown that the above-discussed conventional closures leave much to be desired. One of the gravest problems which is encountered during the use of the conventional closures is that, of necessity, temperature differentials exist between various parts of the closure. So, for instance, different temperature prevail in different regions of the coking chamber during the coking operation and, consequently, also the portions of the closure which are contiguous with such regions will be at different temperatures. Thus, for example the temperature of the lower portions of the frame and of the door will be lower than that of the upper portion. Also, the outlaying zones of the closure will be at a lower temperature than the zones which are closer to the source of heat, that is, the coal being coked.
As a result of these temperature differentials, the coal gas containing volatile by-products of the coking operation, such as tar or pitch vapors, which will penetrate into the clearance between the door and the frame, will be subjected to cooling in the clearance to a temperature below that at which the pitch or tar vapors condense, or even below the temperature at which the liquid pitch or coal tar solidify. This will result in the formation of incrustations at some zones of the closure.
These incrustations are very disadvantageous in that they can interfere with the sealing of the clearance between the door and the frame so that the tar or pitch vapors which are noxious and create health hazards can escape into the environment of the coking oven. This disadvantage is particularly pronounced when the incrustations form, as they will because of the relatively low temperature prevailing there, at the sealing arrangement which seals the clearance.
To eliminate the disadvantageous effects of the formation of incrustations, and in particular in order to obtain sufficient seal for the clearance between the door and the frame, it was heretofore necessary to remove the incrustations from time to time, with the door removed from the frame, by using special cleaning procedures. It was particularly necessary to remove incrustations from the contact surfaces of the frame and also from the sealing members contacting such contact surfaces in the closed position of the door. These heretofore mandatory cleaning operations involved a considerable time expenditure, and resulted in a not insubstantial mechanical wear and tear of the contact surfaces of the frame as well as of the sealing member. The mechanical influences also regularly result in destruction of the sealing members, so that it was necessary to quite frequently recondition or rebuild one or more of the components which constitute the seal, or even to replace such worn out components by new ones.
To alleviate this situation, it has already been proposed to so construct the seal as to include two separate sealing arrangements, one downstream of the other as considered in the direction of penetration of the coal gas into and through the clearance. One of the sealing arrangements, which is located inwardly and faces the region of the frame which surrounds the opening, may be of metallic material, and the other sealing arrangement which is located radially outwardly of the just mentioned sealing arrangement and which is in contact with the ambient air may be of a packing material. In this proposed construction, the frame is provided with separately situated inner and outer contact surfaces and, in the closing position of the door, the inwardly situated metallic sealing member abuts the inner contact surface and the outer packing member abuts the outer contact surface of the frame. The idea behind this proposed construction was that the packing member would provide for the hermetic sealing of the clearance, while the metallic member would prevent penetration of the volatile by-products of the coking operation to the packing member and thus prevent formation of the incrustations at the latter.
It has also been proposed, in the closure of this type, to offset the external surface of the frame in such a manner that the radially outer contact surface is provided on a step of a greater magnitude than that on which the inner contact surface is provided. The reason for this offset arrangement of these two contact surfaces was to prevent wetting of the outer contact surface by tar which may be able to penetrate between the metallic member and the inner contact surface. Thus, the provision of the outer contact surface on a higher step was supposed to block the flow of the tar onto the outer contact surface. The apparent purpose of this arrangement was not only to prevent soiling of the outer contact surface, but also damage to the packing member. However, experience with the coking ovens using this type of closure has shown that the above-discussed expectations have materialized only to a very limited extent. In particular, it has been established that, despite the above-discussed expedients, it is still necessary to attend to numerous and expensive cleaning operations in the regions of the contact surfaces and of the metallic and packing members.